In U.S. Pat. No. 3,232,678, issued Feb. 1, 1966 to William G. Wilson, and assigned to the assignee of the present application, there is shown and described a brake control valve device that is substantially the same in function and operation as the brake control valve device included in the standard fluid pressure brake apparatus now in use on railway freight cars owned and operated by American railroads. The brake control valve device shown in the above-mentioned U.S. Pat. No. 3,232,678 comprises a service valve portion embodying therein a plurality of slide, spool and disc type valves, and an emergency valve portion that has a slide-type emergency valve slidable on a flat ported valve seat and a graduating valve slidably mounted on a flat ported surface provided therefor on the side of the emergency slide valve opposite the side thereof that engages the flat ported valve seat. This emergency valve portion is operative in response to a service rate of reduction of pressure in a train brake pipe to release fluid under pressure from a quick action chamber to atmosphere at a service rate thereby rendering this emergency valve portion effective to cause an emergency brake application only in response to an emergency rate of reduction of pressure in the train brake pipe.
The manufacture and production of these slide-type valves and valve seats of this emergency valve portion require considerable accurate and skillful machining which, as is readily apparent, increases the cost of the emergency valve portion of which they are an essential component.
Moreover, in U.S. Pat. No. 3,716,276, issued Feb. 13, 1973 to Richard L. Wilson et al, and assigned to the assignee of the present application, there is shown and described a brake control valve device that is substantially the same in function and operation as the latest design of brake control valve devices now being offered to the railway industry as the brake control valve device included in the standard fluid pressure brake apparatus installed on any new freight cars built subsequent to Jan. 1, 1977. In this brake control valve device, the fluid under pressure released from the quick action chamber, when effecting a service brake application, is used to operate a continual quick service valve device that effects a "quick service" transmission through a train brake pipe of a pressure reduction wave.
The above-mentioned continual quick service valve device operates repeatedly in cycles to release locally on each railway vehicle provided with this valve device fluid under pressure from the brake pipe to atmosphere so long as a relay valve device embodied in a brake valve device on the locomotive effects a release of fluid under pressure from the train brake pipe to atmosphere via a choke at a normal rate of brake pipe pressure reduction.
However, if the rate of release of fluid under pressure from the train brake pipe exceeds a normal service rate and approaches, but is less than, an emergency rate, this continual quick service valve device is ineffective to operate in repeated cycles for the reasons given below.
The emergency slide valve and the emergency graduating valve, which are operated by an abutment subject on one side to the pressure in the brake pipe and on the other side to the pressure in the quick action chamber, are so constructed as to release fluid under pressure from the quick action chamber at the same rate as fluid under pressure is released from the train brake pipe.
Consequently, when the rate of release of fluid under pressure from the train brake pipe is greater than the normal rate but less than an emergency rate, the quantity or amount of fluid under pressure supplied from the quick action chamber to the continual quick service valve device via the emergency graduating valve for operating this continual quick service valve device is correspondingly increased. This increased amount of fluid under pressure is supplied through the pipe 13, passageway 115 and bore 120 to the lower side of the diaphragm 77 shown in FIG. 3 of the above-mentioned U.S. Pat. No. 3,716,276 to deflect this diaphragm upward to unseat it from the annular valve seat 119. It is apparent from FIG. 3 that upon the unseating of this diaphragm 77 from the valve seat 119, fluid under pressure flows from the bore 120 into the chamber 125 below the diaphragm 77 and thence to atmosphere via the passageway 122 and choke 123 at a rate determined by the size of this choke which in the brake control valve device now being sold for installation on freight cars used by American railroads has an actual diameter of 0.015625 inch. This being a choke of small size, it so restricts the flow of fluid under pressure from the chamber 125 shown in FIG. 3 that, upon an excessive supply of fluid under pressure to this chamber 125, the continual quick service valve device becomes inoperative to operate in cycles to locally release fluid under pressure from the train brake pipe to atmosphere so long as fluid under pressure is being released from the train brake pipe by the relay valve device embodied in the brake valve device on the locomotive.
Furthermore, it is apparent that when this continual quick service valve device operates in repeated cycles in response to a normal rate of brake pipe reduction, this cyclic operation produces excessive wear of the various elements, especially the valves and valve seats, of this valve device which wear, of course, is undesirable.
Accordingly, it is the general purpose of this invention to provide a railway car brake control valve device with a novel emergency valve portion that embodies a first movable abutment, subject on its respective opposite sides to the pressure in a train brake pipe and in a quick action chamber that is effective, upon a normal service rate of reduction of the pressure in the train brake pipe, to unseat a poppet-type valve from one of two coaxial spaced-apart valve seats between which it is so disposed that, while unseated from both seats, fluid under pressure is released from a quick service volume previously charged from the train brake pipe and disposed on one side of a diaphragm-type valve that is operatively responsive to the venting of fluid under pressure from this quick service volume to effect the release of fluid under pressure from the quick action chamber and the chamber on one side of the first abutment to atmosphere at a rate faster than a normal service rate to cause joint cyclic operation of the abutment-operated poppet valve and the diaphragm-type valve to successively release fluid under pressure from the quick service volume at a certain rate and from the quick action chamber at a faster rate and thereafter recharge this quick service volume from the brake pipe so long as fluid under pressure is released from the train brake pipe at a normal service rate.
An emergency piston disposed within the quick service volume cooperates with the diaphragm valve in response to an emergency rate of reduction of the pressure in the train brake pipe to effect operation of a second movable abutment that constitutes a brake pipe vent valve and a poppet-type valve which effects the supply of fluid under pressure from an emergency reservoir to a brake cylinder simultaneously with the supply from an auxiliary reservoir by operation of the service portion of the control valve device to cause an emergency brake application.